Fluoroalkyl-thiirane compounds and their preparation



United States 3,136,781 FLUOROALKYL :l l NE COLMPOUNDS AND THER-PREPARATION William J. Middleton, Wilmington, Del., assignor to E. I. duPont de l emtours and Company, Wilmington, Del, a corporation ofDelaware N Drawing. Filed Apr. 14, 1961, Ser. No. 102,952 13 Claims.(Cl. 260-327) No thiiranes having polyfiuoroalkyl substituents have beendescribed, in spite of the ever-increasing scientific and technicalinterest in fluorine-containing organic compounds.

The new compounds made available by this invention are the substitutedthiiranes represented by the general formula in which from two to fourof the R groups are polyfluoroalkyl radicals of the class ofperfiuoroalkyl, wchloroperfluoroalkyl and w-hydroperfluoroalkyl, and anyremaining R groups are hydrogen, fluorine, chlorine, hydrocarbyl oralkoxycarbonyl, with the proviso that when R and R are polyfluoroalkyl,R and R are both polyfluoroalkyl, fluorine or chlorine, and that when Rand R are polyfluoroalkyl, R and R are polyfluoroalkyl, hydrogen,hydrocarbyl or alkoxycarbonyl and not more than one of R and R isalkoxycarbonyl.

The terms used above have their normal significance, i.e., aperfluoroalkyl radical is an alkyl radical containing only carbon andfluorine atoms, and an w-chloroperfluoroalkyl or w-hydroperfluoroalkylradical is an alkyl radical containing only carbon and fluorine atomsand one chlorine or hydrogen atom, this chlorine or hydrogen atom beingat the end of the chain. For the sake of brevity, the compounds of theinvention will be referred to as fluoroalkylthiiranes.

These compounds are prepared by one or the other of the followingprocesses:

(A) The compounds of Formula I where the R and R substituents are bothpolyfluoroalkyl (i.e., perfluoroalkyl, w-chloroperfiuoroalkyl orw-hydroperfluoroalkyl) and the other two substituents are bothpolyfluoroalkyl as defined, fluorine or chlorine, are prepared by apyrolysis process which comprises heating at a temperature of at least300 C. a 1,1-dioxo-1,3-dithietane of the general formula (II) R1 SO: R3

atent "ice wherein R and R are both polyfluoroalkyl as defined and R andR are both polyfluoroalkyl, fluorine or chlorine. This pyrolysis processforms the correspondingly substituted thiirane with liberation of sulfurdioxide, in accordance with the equation B so: R R R which may be adiazohydrocarbon (R and R being hydrogen, alkyl, aryl or alkaryl), or anu-diazoester (R being hydrogen or hydrocarbon as above and R beingalkoxycarbonyl, i.e., --COOR Where R is alkyl). This reaction may berepresented by the following equation:

To illustrate, when the diazo compound is diphenyldiazomethane, theresulting thiirane is I'l 00H, R -od-o m s and when it is ethyldiazoacetate, the resulting thiirane is R: H I I R1O -oooorr5 Thepolyfluorinated starting materials for use in process (A) or (B) are,for the most part, themselves new compounds whose synthesis is describedin several copending US. patent applications assigned to the assignee ofthe present application.

In process (A), the starting materials are thepolyfluoroalkyl-substituted 1,1 dioxo-1,3 dithietanes corresponding toFormula II above. These cyclic sulfide-sulfones are fully described andclaimed in the copending U.S. application of Rudolph A. Carboni andJames C. Kauer, Serial No. 45,305, filed July 26, 1960, now U.S. Patent3,058,993. In brief, the cyclic sulfide-sulfones are prepared byoxidation with a mixture of chromium trioxide and yellow fuming nitricacid (nitric acid of specific gravity r1 about l.46-1.5l) of thecorresponding polyfluoroalkyl-substituted 1,3-dithietanes of formulawhereby only one of the intracyclic sulfur atoms is converted' to asulfone group. from 1.25 to 6 moles of chromium trioxide per mole of1,3-dithietane; the nitric acid is used in a molar ratio (as HNO between4:1 and :1 with respect to the chromium trioxide; and the reactiontemperature is in the range of 20-150 C. The resulting cyclic sulfone isseparated from the reaction mixture by pouring the latter into water,which dissolves the inorganic materials but not the sulfone.

, The suitable 1,3-dithietanes include the following classes ofcompounds: 7 I

' (1) The 2,4-bis(perfluoroa1kyl, w-chloroperfluoroalkyl, orw-hydroperfluoroalkyl)-2,4 dichloro 1,3 dithietanes. These componds,which are dimers of fluorothioacyl chlorides, are fully described'andclaimed in my copending U.S. application Serial'No. 833,913, filedAugust 17, 1959. They are prepared by ultraviolet light irradiation,preferably in a chlorofluorocarbon solvent, of the fluorothioacylchlorides of the formula where X is fluorine, chlorine or hydrogen, andR; is a perfluoroalkylene radical. The fluorothioacyl chloridesthemselves may be prepared by reaction with the vapors of boiling sulfurof a fluorochloroalkane XR -CCl or of a chlorofluoroalkylmercurycompound r- 2)2 where X and K: have the previously indicatedsignificance.

Examples of 1,3-dithietanes of this class are CFa S CF3 C2195 S CzFs03171 S S Cl C S Cl and (3) The tetrakis (perfluoroalkyl,w-chloroperfluoroalkyl, or w-hydroperfluoroalkyl)-1,3-dithietanes. Thesecompounds are either described in the literature or can be referably,there is used 4 i prepared by spontaneous dimerization, preferably inthe presence of a Lewis base such as dimethylformamide or.

a hydrocarbon ether, of the corresponding di(polyfluoroalkyl)thioketonesas described and claimed in my copend ing U.S. application Serial No.791,860, filed February 9, 1959, now U.S. Patent 3,069,396. The latter,which are fully described and claimed in my copending joint U.S.

application with Edward G. l-Ioward, Serial No. 791,857, filed February9, 1959, nowfU.S. Patent 3,970,173, can be prepared by heatingdi(polyfluoroalkyl)ketones with phosphorus pentasulfide at ZOO-300 C.Theymay also be prepared by reacting molten sulfur at 400-650 C. with apolyfluoroolefin of at least three carbon atoms accordance with theequation RCF=OFO FR is RCHflfiCliiR I v s V I or by reacting hotphosphorus pentasulfide with a secondary polyfluoroalkyl iodide of atleast three carbon atoms in accordance with the equation p, vnomorrorn1+ ms, 'RCE3C.CF2R

(CF R in these equations being perfiuoroalkyl, w-chloroperfluoroalkyl orw-hydroperfluoroalkyl).

Examples of 1,3-dithietanes of this class are:

Oxidation of the 1,3-dithietanes of classes (1), (2) and (3) by themethod described above leads to the corresponding 1,l-dioxo-l,3dithietanes, that is, to the compounds exemplified by theformulas shown for each of these classes, except that one of the sulfuratoms is '1'6- placed by a sulfone group (--SO The preferredpolyfiuoroalkyl-substituted 1,1'-dioxo-1,3-dithietanes for good yieldsat 500-600 C. with shorter contact times,

Higher temperatures can be used but it is in general un-' desirable toexceed about 700 C. since appreciable de composition of thefluoroalkylthiirane with loss of sulfur and formation of thecorresponding fluoroalkylethylene begins to take place in theneighborhood of 650 C. The

pyrolysis is most conveniently conducted by passing va pors of thepolyfiuoroalkyl 1,1 dioxo 1,3 dithietane through a reaction zone held atthe required temperature, for example a tube of heat-resistant glass orceramic or of metal, such as platinum, nickel, stainless steel or Monelmetal. The pyrolysis can be performed at atmospheric pressure, butbetter results are obtained by operating at reduced pressures, e.g., ofthe order of 0.1-100 mm. of mercury. The contact time in the hotreaction zone varies, depending on factors such as the operatingpressure, but it is in general in the range of from 1 to 60 seconds. Thegaseous reaction product emerging from the reaction zone is thencondensed in cold traps and the condensate is distilled to effectseparation of the fluoroalkylthiirane from the sulfur dioxide.Alternatively, the gaseous reaction product can be passed through trapsheld at such a temperature that the fluoroalkylthiirane alone iscondensed while the sulfur dioxide escapes.

In process (B), the starting materials are thedi(polyfiuoroalkyl)thioketones of the formula Thesepolyfluoroalkylthioketones are reacted with diazo compounds of the typeWhere R and R have the previously defined significance. Thus, the diazocompound can be a diazohydrocarbon, examples of which are diazomethane,N CH diazoethane, N CHCH dimethyldiazomethane, N C(CH 1- .diazopropane,N CHC H l-diazobutane,

4-diazo-2-methylbutane, N CHCH CH(CH l-diazoheptane, N CH(CH CHphenyldiazomethane,

N CI-IC H methylphenyldiazomethane, N C(CH (C H diphenyldiazomethane, NC(C H di(p-tolyl)diazomethane, N C (C H CH di (p-butylphenyldiazomethane,

and di-3-naphthyldiazomethane, N C(C H Preferably, any hydrocarbyl grouppresent in the diazohydrocarbon has from 1 to 10 carbon atoms. Stillmore preferably, both R and R are aryl or alkaryl of 6 to 10 carbonatoms. The diazo compound can also be an a-diazoester, examples of whichare: methyl diazoacetate, N CHCOOCH ethyl diazoacetate, N CHCOOC Hisoamyl diazoacetate, N CHCOOCH CH CH(CH n-hexyl diazoacetate, N CHCOOCH ethyl a-diazopropionate, N C(CH )C00C H methyl cz-diazobutyrate,

N C (C H COOCH ethyl ot-diazoisocaproate,

Ngc Z] (360021 1 (3 ethyl a-diazooctanoate, N C[CH (CH CH ]COOC H methylu-diazophenylacetate, N C(C H )COOCH and ethyl et-diazo-(,B-naphthylacetate) N C(C H )COOC H The preferred diazoesters are thoseof the formula where R is hydrogen or hydrocarbyl of 1 to 10 carbonatoms and R is an alkoxycarbonyl group --COOR where R is alkyl of 1 to 6carbon atoms.

The reaction between the polyfiuoroalkylthioketone and the diazocompound is conducted simply by bringing the two reactants in contact,preferably but not necessarily in approximately equimolar amounts. Thereaction is vigorous and exothermic. For this reason, it is generallycarried out at an external temperature between about -100 and +20 C. andwhich is preferably in the range from to 0 C. A solvent for thereactants can be used if desired to moderate the vigor of the reaction.Suitable solvents are, for example, the aliphatic and aromatichydrocarbons, the acyclic or cyclic ethers, etc. The reaction is mostconveniently carried out at atmospheric pressure, allowing the nitrogenthat forms to escape,

but closed vessels can be used if desired. The reaction is rapid andgives good yields of the resulting polyfluoroalkylthiirane, which can beisolated and, if necessary, purified by conventional procedures.

The following examples illustrate the invention in greater detail.

EXAMPLE 1 1,1 dioxo 2,2,4,4-tetrakis(triiluoromethyl)-1,3-dithietane wassublimed at 1 mm. pressure and at the rate of 20 g. per hour through aplatinum tube 0.5 inch in diameter and 25 inches long, heated to 550 C.over a length of 12 inches. The effluent gases were condensed in a trapcooled by liquid nitrogen. The condensate was then distilled through apacked column. From 99 g. of starting material was obtained 15.2 g. ofsulfur dioxide, B.P. --11 to 9 C. and further identified by infraredspectroscopy, and 79.1 g. of 2,2,3,3-tetrakis(trifluoro methyl)thiiraneas a colorless liquid, B.P. 91 C., 11 1.3164.

Analysis.Calcd. for C F S: C, 21.70; F, 68.65; S, 9.65. Found: C, 21.89;F, 68.54; S. 9.65.

When the pyrolysis was carried out at 650 C. instead of 550 C., anequimolar mixture of the thiirane and oftetrakis(trifluoromethyl)ethylene was obtained.

The 1,1 dioxo-2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithietane used asthe starting material in this example may be prepared as follows:

(A) Perfluoropropanethione In a platinum tube heated at 432-625 C. wasintroduced a mixture of hexafluoropropene (34 g.) and molten sulfur (26ml.) over a period of 1.5 hours. The volatile reaction product wascondensed in a trap at -S0 C. Distillation of this condensate from thetrap at 1 mm. pressure gave the deep blue perfiuoropropanethione,

(B) 2,2,4,4-Tetrakis( T rifluoromethyl ,3-Dz'ethietanePerfluoropropanethione, 2.4 ml., was placed in a flask and cooled to 80C. A solution of 3 drops of N,N- dimethylformamide in 5 ml. of diethylether was added. The blue color of the perfluoropropanethione fadedinstantly and a white crystalline precipitate formed in a few minutes.The mixture was allowed to warm to room temperature and then distilled.There was obtained 2.1 g. of2,2,4,4-tetrakis(trifluorome'thyl)-l,3-dithietaue,

or, s or,

063 \S/ \CF3 as a clorless liquid boiling at l091ll C.

(C) 1,1-Dix0-2,2,4,4-Tetrakis(Trifluoromethyl) 1,3-Dithietane A mixtureof 91 g. of 2,2,4,4-tetrakis(trifluoromethyl) 1,3-dithietane, 150 ml. ofyellow fuming nitric acid and 60 g. of chromium trioxide'was heated atreflux (about 70 C.) for hours. The reaction mixture was then pouredover 250 g. of crushed ice, and the solid that separated was collectedon a filter under nitrogen pressure, washed with water andrecrystallized from methanol. After drying, there was obtained 80.1 g.of 1,1-dioxo- 2,2,4,4-tetrakis(trifluoromethyl) -1,3-dithietane,

as large colorless prisms, M.P. 35 C., 11 1.3438.

Analysis.-Calcd for C F O S C, 18.19; F, 57.54;

C, 17.91; F, 57.82; S, 16.38.

7 EXAMPLE II Using the apparatus and conditions of Example 1, ex: ceptthat the pyrolysis temperature was 525 C., 40 g. of1,l-dioxo-2,4-bis(chlorodifluoromethyl)-2,4-difluoro-1, 3 -dithietanewas pyrolyzed over a period of 2 hours. The condensate in the cold trapwas then distilled under reduced pressure to give 27.85 g. of2,3-bis(ch1orodifluoromethyl) -2, 3-diffuorothiir ane,

S, 16.11. Found:

(A) 2,4-Bis(Chlorodifluoromethyl)-2,4-Diflu0r0- 1,3-Dithietane Asolution of 38 g. of chlorodifluorothioacetyl fluoride [preparedaccording to J. Gen. Chem. U.S.S.R.--Eng. Tr. 27, 2301, (1957)] in ml.of dichlorodifluoromethane in a quartz reaction vessel was irradiated atreflux temperature with ultraviolet light for 3 hours. Thedichlorodifluoromethane was evaporated and the residue was distilledunder reduced pressure. There was obtained 31.3 g. of2,4-bis(chlorodifluoromethyl)-2,4-difluoro-1,3-dithietane as a colorlessoil, B.P. 44 C. at 23 mm. pressure, n 1.4131.

(B) 1,1-Di0x0-2,4-Bis(Chlorodifluoromethyl) 2,4-Diflu0- r0-1,3-Dithietane A mixture of 118.8 g. of 2,4-bis(chlorodifluorornethyl)-2,4-difiuoro-1,3-dithietane (cis and trans isomers), 96 g. of chromiumtrioxide and 240 ml. of yellow fuming nitric acid was stirred and heatedto reflux (about 70 C.) for 18 hours. The reaction mixture was cooledand filtered and the filtrate was poured over 500 g. of crushed ice. Thelower organic layer was separated, washed with water, dried over calciumchloride and distilled under reduced pressure. There was obtained 99.4g. of-1,1-dioxo- 2,4-bis (chlorodifluoromethyl-2,4-difluoro-1,3-dithietane,

as a colorless liquid, B.P. 50.5 C. at 8 mm. pressure, n 1.4169. Thefluorine nuclear magnetic resonance spectrum indicated this product tobe a mixture of the cis and trans isomers in approximately equalamounts.

Analysis.-Calcd for C C1 F O S C, 14.60; Cl, 21.55; F, 34.64; S, 19.50.Found: C, 14.84; Cl, 21.49; F, 34.54; S, 19.52.

EXAMPLE HI Using the'apparatus and conditions of Example I, ex

cept that the reaction temperature was 530 C. and the pressure withinthe tube 2 m., 25 'g. of 1,l-dioxo2,4-bis5 (trifluoromethyl)-2,4-difluoro -l ,3 -dithietane was pyrolyzed over a period of one hour.Distillation of the condensed reaction product gave sulfur doxide and11.5 g. of 2,3-

bis(trifluoromethyl)-2,3-difluorothiirane,

' F F oF.-,o- CF3 asa liquid boiling at 35-36" C., 11 9 1.297.

Analysis.--Calcd for C F S: C, 20.7; F, 65.6; 8, 13.7

Found: C, 22.1; F, 65.7; S, 13.4. V a .7

Gas chromatographic analysis showed this product to be a 50:50 mixtureof the cis and trans isomers.

The 1,1-dioxo-2,4-bis(trifluoromethyl)-2,4-difluoro-l,3- diethietaneused as the startingmaterial in this example may be prepared as follows:

(A) 2,4-Bis(Trifluoromethyl)-2,4-Difluor0- 1,3-Dithietane A quartzreaction vessel equipped with a condense cooled with solid carbondioxide was swept with nitrogen and charged with 25 ml. (as liquid) ofdichlorodifluoromethane and 15 g. of trifluorothioacetyl fluoride. Thevessel was irradiated with a mercury resonance lamp for 3 hours, afterwhich the yellow color of the trifluorothioacetyl fiuoride haddisappeared. The volatile materials were allowed to escape at roomtemperature, leaving 11.5 g. of a light yellow liquid which, onfractional distillation, yielded 9 g. of2,4-bis(trifluoromethyl)2,4-difluoro- 1,3-dithietane, B.P. 69 C., n1.3378.

Analysis.-Calcd for C F S C, 18.2; F, 57.6. Found: C, 18.3; F, 57.6.

(B) 1 ,1 -Di0x0-2,4-Bis(Triflubromethyl) -2,4-Diflu0r0-1,3- Dithietane Amixture of 60 g. (0.23 mole) of2,4-bis(trifluoromethyl)-2,4-difluoro-1,3-dithietane, 113 g. (1.13moles) of chromium trioxide and ml. of yellow fuming nitric acid wasrefluxed for 4 hours and then poured onto a mixture of 'water and ice.The resulting mixture was extracted twice with IOU-ml. portions ofmethylene chloride,

the organic extracts were dried over sodium sulfate and distilled to.give 38.5 g. of l,1-dioxo-2,4-bis(trifluoro methyl) -2,4-difluoro-1,3dithietane,

' 01% S CF;

B.P. 106 C., 11 1.3540.

Analysis.Calcd for C F O S C, 16.2; F, 51.4; S,

21.7. Found: C, 16.8; F, 51.7; S, 21.1.

EXAMPLE IV A solution of 22.8 g. of ethyl diazoacetate in 40 ml. ofpentane was cooled to '-78 C. Perfluoropropanethione was added dropwiseto the stirred solution over a period of 5 minutes until a faint bluecolor persisted. The reaction mixture was filtered while still cold andthe white solid that was collected on the filter was washed with coldpentane and recrystallized from diethyl ether. There was obtained 10.3g. of 2,2-bis-(trifiuoromethyl)- 3 (ethoxycarb onyl) thiirane,

as white needles, M.P. 84-86 C. An analytical sample was prepared byrecrystallizing again from ether to give white needles, M.P. 87-89 C.

Analysis.Calcd for C7H6F2O2SZ C, 31.38; H, 2.26; F, 42.51; S, 11.95.Found: C, 31.52; H, 2.02; F, 42.25; S, 12.10.

EXAMPLE V Diphenyldiazomethane was prepared in solution as follows: Amixture of 19.6 g. (0.1 mole) of benzophenone hydrazone, 22 g. (0.1mole) of yellow mercuric oxide, and 100 ml. of pentane was stirred for 6hours at room temperature. Magnesium sulfate, 20 g., was added and thesuspension was stirred for an additional 20 minutes and then filtered.The solids were washed with 25 ml. of pentane and this wash was combinedwith the filtrate. The bright purple filtrate was then transferred to aflask and cooled to 78 C. To this solution, containingdiphenyldiazomethane, was added dropwise with vigorous stirring 18.2 g.(0.1 mole) of perfluoropropanethione and strong external cooling wasmaintained during the entire time of the addition. A vigorous evolutionof gas ccured and a solid began to separate after about one-third of theperfluoropropanethione had been added. When the addition was completed,the reaction mixture was allowed to warm to room temperature and thesolvent was evaporated under reduced pressure. There was obtained 35 g.of slightly damp crystalline residue, which was recrystallized frompentane to give 22 g. of 2,2-bis(trifluoromethyl) -3,3-diphenylthiirane,

as white needles, M.P. 79-80 C. A second crop of g. of crystals was alsoobtained from the filtrate of these recrystallizations.

Analysis.Calcd' for C I-1 1 5: C, 55.17; H, 2.90; F, 32.73; S, 9.20;M.W., 348.3. Found: C, 54.37; H, 2.95; F, 32.71; S, 9.29; M.W., 354.

While the invention has been illustrated in the foregoing detailedexamples with reference to certain specific product, it is generic tothe fluoroalkylthiirane represented by Formula I shown and explainedearlier. These compounds can be more specifically divided into thefollowing three groups:

(I-a) The compounds of the formula where R and R are polyfiuoroalkylradicals (perfluoroalkyl, w-chloroperfluoroalkyl andw-hydroperfiuoroalkyl), preferably of 1 to 6 carbon atoms, and R and Rare both polyfiuoroalkyl radicals as defined, preferably of 1 to 6carbon atoms, fluorine or chlorine. Additional examples of suchcompounds, which can be prepared by the process of Examples I-III,include 2,3-bis (perfluoroethyl)- 2,3-dichlorothiirane;2,3-bis(w-chloroperfluorobutyl)-2,3- 'dichlorothiirane; 2,3 bis(whydroperfluorohexyl)-2,3-dichlorothiirane; 2,3-bis (perfluoropropyl) 2,3difluorothiirane; 2,3bis(w chloroperfluoropropyl) 2,3 difluorothiirane;2,3-biS(w hydroperfiuorobutyD-Z,3-difiurothiirane; 2,2,3,3-tetrakis(perfluorobutyl) thiirane; 2,3-bis (perfluorobutyl) -2,3-bis(trifluoromethyl) thiirane; 2,3-bis w-ChlOl'O- toperfiuoroethyl)-2,3-bis(trifluoromethyl)thiirane; and the like.

(I-b) The compounds of the formula where R and R are polyfluoroalkylradicals (perfluoroalkyl, w-chloroperfluoroalkyl andw-hydroperfluoroalkyl), preferably of 1 to 6 carbon atoms, R is hydrogenor a hydrocarbyl radical (alkyl, aryl, alkaryl), preferably of 1 to 10carbon atoms; and R is an alkoxycarbonyl radical, i.e., COOR Where R isalkyl, preferably of 1 to 6 carbon atoms. Additional examples of suchcompounds, which can be prepared by the process of Example IV, include2,2-bis(perfluoroethyl)-3-(hexyloxycarbonyl)thiirane;2,2-bis(pertluorohexyl) 3 methyl-3- ethoxycarbonyl thiirane; 2,2-bisw-chloroperfluoropropyl -3-ethyl-3- (methoxycarbonyl thiirane; 2,2-bis(chlorodifiuoromethyl -3-hexyl-3- (ethoxycarbonyl thiirane; 2,2- bisw-hydroperfluorobutyl -3- (methoxycarbonyl) thiirane; 2trifluorornethyl-Z-perfluoroethyl-3-phenyl-3-(methoxycarbonyl) thiirane;2,2-bis w-hydroperfluoroethyl -3-naphthyl-3-(ethoxycarbonyl)thiirane;and the like.

(Ic) The compounds of the formula where R and R are polyfiuoroalkylradicals (perfluoroalkyl, w chloroperfluoroalkyl, whydroperfluoroalkyl), preferably of 1 to 6 carbon atoms, and R and R arehydrogen or hydrocarbyl radicals (alkyl, aryl, alkaryl), preferably of 1to 10 carbon atoms. Still more preferably, both R and R are aryl oralkaryl radicals of 6 to 10 carbon atoms. Additional examples of suchcompounds, which can be prepared by the process of Example V, include2,2-bis(trifluoromethyl)-3-methylthiirane; 2- trifluoromethyl-2-(wchloroperfluoroethyl)-3,3-dimethylthiirane;2,2-bis(trifluoromethyl)-3-propylthiirane; 2,2-bis(perfluorohexyl)-3-phenyltl1iirane; 2,2-bis(w-chloroperfluorobutyl-3-rnethyl-3-phenylthiirane; 2-trifluoromethyl-2- (whydroperfiuoroethyl)-3,3-bis(p-tolyl)thiirane; 2,2-bis (trifluoromethyl)-3,3-bis (p-butylphenyl) thiirane; 2,2-bis (w-hydroperfluorobutyl -3,3-bis a-naphthyl thiirane; and the like.

The fluoroalkylthiiranes of this invention are generically useful assolvents or plasticizers for highly halogenated polymers. With thosethiiranes which are liquids at or near ordinary temperature, thesolutions so obtained can be used to impregnate porous materials such astextiles, paper, wood, brick, etc., thereby obtaining waterproofingeffects, and to apply protective coatings on non-porous materials suchas metals. For example, solutions containing about 5% by weight of lowmolecular weight polytetrafiuoroethylene (M.P. 83-105 C.) in2,2,3,3-tetrakis (trifiuoromethyl)thiirane and in2,3-bis(chlorodifluoromethyl)-2,3-difiuorothiirane were prepared bystirring mixtures of the polymer and the solvent at room temperature.When the homogeneous solutions were coated on filter paper, the waterrepellency of the treated paper was considerably improved in comparisonwith untreated controls. Fluoroalkylthiiranes which are normally solidare also excellent solvents at or above their melting points forpolyhalogenated polymers. For example,2,2-bis(trifluoromethyl)-3,3-diphenylthiirane dissolved readily the samepolytetrafiuoroethylene at C. Thus, there can be obtained plasticizedpolymer compositions useful for making tight seals on threaded joints,valves, couplings, fittings and similar metallic parts.

The liquid thiiranes are further suitable for use in low or moderatetemperature thermometers. Thus, 2,2,3,3-tetrakis(trifluoromethyl)thiirane in a sealed glass capillary tube wasfound to be superior to alcohol as a temperature 11 indicator because ofits highercoefiicientof, expansion, and superior to mercury in that itcan be used at lower temperatures.

The foregoing detailed discription has been given for clearness ofunderstanding only and no unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed, for obvious modifications will occur to those skilled in theart. v V

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A compound of the formula wherein from 2 to 4 of the R groups arepolyfiuoroalkyl radicals of from 1 to 6 carbon atoms and selected fromthe class consisting of perfluoroalkyl, w-chloroperfluoroalkyl andw-hydroperfiuoroalkyl, and any remaining R groups are selected from theclass consisting of hydrogen, fluorine, chlorine, monovalent hydrocarbylradicals selected from the class consisting of alkyl of 1 to 6 carbonatoms and aryl and alkaryl of 6 to 10 carbon atoms, and monovalentalkoxycarbonyl radicals in which the alkoxy groups have from 1 to 6carbonatoms; with the provisos that (1) when R and R are polyfluoroalkylradicals as defined above, R and R are both members of one of the threegroups selected from the class consisting of (a) polyfiuoroalkylradicals as defined above, (b) fluorine and (c) chlorine; and (2) when Rand R rare polyfluoroalkyl radicals as defined above, R and R aremembers of the class consisting of polyfluoroalkyl radicals as definedabove, hydrogen, hydrocarbyl radicalsv as defined above, andalkoxycarbonyl radicals as defined above, not more than one of R and Rbeing alkoxycarbonyl.

2. A compound of the formula wherein said perfluoroalkyl radicals havefrom 1 to 6 carbon atoms.

3. A compound of the formula wherein said perfluoroalkyl radicals havefrom 1 to 6 carbon atoms. a

4. A compound of the'formula V H v I (perfluoroalkyl) -CCC O Oalkyl 2wherein said perfiuoroalkyl, radicals have from 1 06 carbon atoms; andsaid alkyl radical has from 1 to 6 carbon atoms 5. A compound oftheformula r yl).

carbon atoms, and said aryl radicals have from 6 to 10 carbon atoms.

6.. 2,2,3,3-tetrakis(trifiuoromethyl)thiiraneQ I I 7.2,3-bis(chlorodifluoromethyl)-2,3-difluorothiirane. 8.2,3-bis(trifluoromethyl)-2,3-difluorothiirane.

9 2 ,Z-bis (trifluoromethyl -3 (ethoxycarbonyl) thiirane, V i

10. 2,2-bis(trifluoromethyl)-3,3 diphenylthiirane.

11. Process which comprises heating at a temperature of at least 300 C.a 1,l-dioXo-l,3-dithietane of the formula l R1 /S02, /R3

V '7 i wherein R and R are polyfluoroalkyl radicals of from 1 m6 carbonatoms ,and selected from the class consisting of perfluoroalkyl,w-chloroperfluoro'alkyland w-hydropere fiuoroalkyl radicals, and R and Rare both members of one of the groups selected from the class consistingor polyfluoroalkyl radicals as defined above, fluorine and chlorine,whereupon sulfur dioxide is liberated and a fluoroalkylthiirane isobtained. 7 e e .12. The process of claim 11 in which vapors of said1,l-dioxo-l,3-dithietane are passed through a reaction zone held at atemperature between about 300 and 700 C. 13. The process of claim 11 inwhich the pyrolysis is etfected at a pressure of from 0.1 to 100 mm. ofmercury.

. References Cited in the'file of this patent UNITED STATES PATENTS2,724,719 Markley et al Nov. 22, 1955

1. A COMPOUND OF THE FORMULA
 11. PROCESS WHICH COMPRISES HEATING AT ATEMPERATURE OF AT LEAST 300*C. A 1,1-DIOXO-1,3-DITHIETANE OF THE FORMULA